Hi uditgopalka,
The
OG books are great sources for practice questions, but they're not designed to teach you Tactics, patterns or the little 'secrets' behind the GMAT - for those, you will need Course-oriented materials. Assuming that you took your CATs in a realistic fashion that matches-up how you will take the Official GMAT - and your 550 is an accurate result - then you will have to put in some significant additional study time before you will be able to hit your Score Goal.
Raising a 550 to the point that you can consistently score 700+ will likely require at least another 3 months of consistent, guided study - and you will have to make significant improvements to how you handle BOTH the Quant and Verbal sections. Thankfully, the GMAT is a consistent, predictable Exam, so you CAN train to score at a higher level. That having been said, you might want to consider pushing back your Test Date.
I mentioned this in a prior post, but it bears repeating: if you are interested in applying to any highly-competitive Schools, then you would likely find it beneficial to speak with an Admissions Expert about your overall profile and plans. Those Experts should be able to answer your Admissions questions and help define the specific areas of your profile that could use some improvement.
There's a Forum full of those Experts here:
https://gmatclub.com/forum/ask-admissio ... tants-124/1) What are the exact application deadlines that you are considering?
GMAT assassins aren't born, they're made,
Rich